X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcTyClsDecls.lhs;h=0da4dafd5857026265c980983308660738048bc7;hb=6942766ac64f71b57c85a4069900b383495e2bdb;hp=0ff60b66c68b88123cfece01d4c3ea499fa2fb7f;hpb=2f51f1402e6869c0f049ffbe7b019bf6ab80558f;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcTyClsDecls.lhs b/ghc/compiler/typecheck/TcTyClsDecls.lhs index 0ff60b6..0da4daf 100644 --- a/ghc/compiler/typecheck/TcTyClsDecls.lhs +++ b/ghc/compiler/typecheck/TcTyClsDecls.lhs @@ -1,282 +1,241 @@ % -% (c) The AQUA Project, Glasgow University, 1996 +% (c) The AQUA Project, Glasgow University, 1996-1998 % \section[TcTyClsDecls]{Typecheck type and class declarations} \begin{code} -#include "HsVersions.h" - module TcTyClsDecls ( - tcTyAndClassDecls1 + tcTyAndClassDecls ) where -import Ubiq{-uitous-} +#include "HsVersions.h" -import HsSyn ( TyDecl(..), ConDecl(..), BangType(..), - ClassDecl(..), MonoType(..), PolyType(..), - Sig(..), MonoBinds, Fake, InPat, HsBinds(..), Bind, HsExpr ) -import RnHsSyn ( isRnTyCon, RenamedTyDecl(..), RenamedClassDecl(..), - RnName(..){-instance Uniquable-} +import HsSyn ( TyClDecl(..), + ConDecl(..), Sig(..), HsPred(..), + tyClDeclName, hsTyVarNames, tyClDeclTyVars, + isTypeOrClassDecl, isClassDecl, isSynDecl, isClassOpSig ) -import TcHsSyn ( TcHsBinds(..), TcIdOcc(..) ) - -import TcMonad -import Inst ( InstanceMapper(..) ) +import RnHsSyn ( RenamedTyClDecl, tyClDeclFVs ) +import BasicTypes ( RecFlag(..), NewOrData(..) ) +import HscTypes ( implicitTyThingIds ) + +import TcRnMonad +import TcEnv ( TcTyThing(..), TyThing(..), TyThingDetails(..), + tcExtendKindEnv, tcLookup, tcLookupGlobal, tcExtendGlobalEnv, + isLocalThing ) +import TcTyDecls ( tcTyDecl, kcConDetails ) import TcClassDcl ( tcClassDecl1 ) -import TcEnv ( tcExtendTyConEnv, tcExtendClassEnv, - tcExtendGlobalValEnv, - tcTyVarScope, tcGetEnv ) -import TcKind ( TcKind, newKindVars ) -import TcTyDecls ( tcTyDecl, mkDataBinds ) - -import Bag -import Class ( Class(..), getClassSelIds ) -import Digraph ( findSCCs, SCC(..) ) -import Name ( getSrcLoc ) -import PprStyle -import Pretty -import UniqSet ( UniqSet(..), emptyUniqSet, - unitUniqSet, unionUniqSets, - unionManyUniqSets, uniqSetToList ) -import SrcLoc ( SrcLoc ) -import TyCon ( TyCon, tyConDataCons, isDataTyCon ) -import Unique ( Unique ) -import Util ( panic, pprTrace ) - +import TcInstDcls ( tcAddDeclCtxt ) +import TcMonoType ( kcHsTyVars, kcHsType, kcHsLiftedSigType, kcHsContext, mkTyClTyVars ) +import TcMType ( newKindVar, zonkKindEnv, checkValidTyCon, checkValidClass ) +import TcUnify ( unifyKind ) +import TcType ( Type, Kind, TcKind, mkArrowKind, liftedTypeKind, zipFunTys ) +import Type ( splitTyConApp_maybe ) +import Variance ( calcTyConArgVrcs ) +import Class ( Class, mkClass, classTyCon ) +import TyCon ( TyCon, ArgVrcs, AlgTyConFlavour(..), DataConDetails(..), visibleDataCons, + tyConKind, tyConTyVars, tyConDataCons, isNewTyCon, + mkSynTyCon, mkAlgTyCon, mkClassTyCon, mkForeignTyCon + ) +import TysWiredIn ( unitTy ) +import Subst ( substTyWith ) +import DataCon ( dataConOrigArgTys ) +import Var ( varName ) +import FiniteMap +import Digraph ( stronglyConnComp, SCC(..) ) +import Name ( Name ) +import NameEnv +import NameSet +import Outputable +import Maybes ( mapMaybe ) \end{code} + +%************************************************************************ +%* * +\subsection{Type checking for type and class declarations} +%* * +%************************************************************************ + The main function ~~~~~~~~~~~~~~~~~ \begin{code} -data Decl = TyD RenamedTyDecl | ClD RenamedClassDecl - -tcTyAndClassDecls1 :: InstanceMapper - -> Bag RenamedTyDecl -> Bag RenamedClassDecl - -> TcM s (TcEnv s, TcHsBinds s) +tcTyAndClassDecls :: [RenamedTyClDecl] + -> TcM [TyThing] -- Returns newly defined things: + -- types, classes and implicit Ids -tcTyAndClassDecls1 inst_mapper rnty_decls rncls_decls - = sortByDependency syn_decls cls_decls decls `thenTc` \ groups -> - tcGroups inst_mapper groups +tcTyAndClassDecls decls + = tcGroups (stronglyConnComp edges) where - cls_decls = mapBag ClD rncls_decls - ty_decls = mapBag TyD rnty_decls - syn_decls = filterBag is_syn_decl ty_decls - decls = ty_decls `unionBags` cls_decls + edges = map mkEdges (filter isTypeOrClassDecl decls) - is_syn_decl (TyD (TySynonym _ _ _ _)) = True - is_syn_decl _ = False +tcGroups [] + = returnM [] -tcGroups inst_mapper [] - = tcGetEnv `thenNF_Tc` \ env -> - returnTc (env, EmptyBinds) - -tcGroups inst_mapper (group:groups) - = tcGroup inst_mapper group `thenTc` \ (new_env, binds1) -> - - -- Extend the environment using the new tycons and classes - tcSetEnv new_env $ - - -- Do the remaining groups - tcGroups inst_mapper groups `thenTc` \ (final_env, binds2) -> - - returnTc (final_env, binds1 `ThenBinds` binds2) +tcGroups (group:groups) + = tcGroup group `thenM` \ (env, new_things1) -> + setGblEnv env $ + tcGroups groups `thenM` \ new_things2 -> + returnM (new_things1 ++ new_things2) \end{code} Dealing with a group ~~~~~~~~~~~~~~~~~~~~ -\begin{code} -tcGroup :: InstanceMapper -> Bag Decl -> TcM s (TcEnv s, TcHsBinds s) -tcGroup inst_mapper decls - = --pprTrace "tcGroup: " (ppCat (map (fst.fmt_decl) (bagToList decls))) $ - - -- TIE THE KNOT - fixTc ( \ ~(tycons,classes,_) -> - - -- EXTEND TYPE AND CLASS ENVIRONMENTS - -- including their data constructors and class operations - -- NB: it's important that the tycons and classes come back in just - -- the same order from this fix as from get_binders, so that these - -- extend-env things work properly. A bit UGH-ish. - tcExtendTyConEnv tycon_names_w_arities tycons $ - tcExtendClassEnv class_names classes $ - - -- DEAL WITH TYPE VARIABLES - tcTyVarScope tyvar_names ( \ tyvars -> - - -- DEAL WITH THE DEFINITIONS THEMSELVES - foldBag combine (tcDecl inst_mapper) - (returnTc (emptyBag, emptyBag)) - decls - ) `thenTc` \ (tycon_bag,class_bag) -> - let - tycons = bagToList tycon_bag - classes = bagToList class_bag - in - - -- SNAFFLE ENV TO RETURN - tcGetEnv `thenNF_Tc` \ final_env -> - - returnTc (tycons, classes, final_env) - ) `thenTc` \ (tycons, classes, final_env) -> - - - -- Create any necessary record selector Ids and their bindings - mapAndUnzipTc mkDataBinds (filter isDataTyCon tycons) `thenTc` \ (data_ids_s, binds) -> +Consider a mutually-recursive group, binding +a type constructor T and a class C. + +Step 1: getInitialKind + Construct a KindEnv by binding T and C to a kind variable + +Step 2: kcTyClDecl + In that environment, do a kind check + +Step 3: Zonk the kinds + +Step 4: buildTyConOrClass + Construct an environment binding T to a TyCon and C to a Class. + a) Their kinds comes from zonking the relevant kind variable + b) Their arity (for synonyms) comes direct from the decl + c) The funcional dependencies come from the decl + d) The rest comes a knot-tied binding of T and C, returned from Step 4 + e) The variances of the tycons in the group is calculated from + the knot-tied stuff + +Step 5: tcTyClDecl1 + In this environment, walk over the decls, constructing the TyCons and Classes. + This uses in a strict way items (a)-(c) above, which is why they must + be constructed in Step 4. Feed the results back to Step 4. + For this step, pass the is-recursive flag as the wimp-out flag + to tcTyClDecl1. - -- Extend the global value environment with - -- a) constructors - -- b) record selectors - -- c) class op selectors - - tcSetEnv final_env $ - tcExtendGlobalValEnv (concat data_ids_s) $ - tcExtendGlobalValEnv (concat (map getClassSelIds classes)) $ - tcGetEnv `thenNF_Tc` \ really_final_env -> - - returnTc (really_final_env, foldr ThenBinds EmptyBinds binds) - - where - (tyvar_rn_names, tycon_names_w_arities, class_names) = get_binders decls - tyvar_names = map de_rn tyvar_rn_names - de_rn (RnName n) = n +Step 6: Extend environment + We extend the type environment with bindings not only for the TyCons and Classes, + but also for their "implicit Ids" like data constructors and class selectors - combine do_a do_b - = do_a `thenTc` \ (a1,a2) -> - do_b `thenTc` \ (b1,b2) -> - returnTc (a1 `unionBags` b1, a2 `unionBags` b2) -\end{code} +Step 7: checkValidTyCl + For a recursive group only, check all the decls again, just + to check all the side conditions on validity. We could not + do this before because we were in a mutually recursive knot. -Dealing with one decl -~~~~~~~~~~~~~~~~~~~~~ -\begin{code} -tcDecl :: InstanceMapper - -> Decl - -> TcM s (Bag TyCon, Bag Class) -tcDecl inst_mapper (TyD decl) - = tcTyDecl decl `thenTc` \ tycon -> - returnTc (unitBag tycon, emptyBag) - -tcDecl inst_mapper (ClD decl) - = tcClassDecl1 inst_mapper decl `thenTc` \ clas -> - returnTc (emptyBag, unitBag clas) -\end{code} +The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to +@TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s. -Dependency analysis -~~~~~~~~~~~~~~~~~~~ \begin{code} -sortByDependency :: Bag Decl -> Bag Decl -> Bag Decl -> TcM s [Bag Decl] -sortByDependency syn_decls cls_decls decls - = let -- CHECK FOR SYNONYM CYCLES - syn_sccs = findSCCs mk_edges syn_decls - syn_cycles = [map fmt_decl (bagToList decls) - | CyclicSCC decls <- syn_sccs] - +tcGroup :: SCC RenamedTyClDecl + -> TcM (TcGblEnv, -- Input env extended by types and classes only + [TyThing]) -- Things defined by this group + +tcGroup scc + = -- Step 1 + mappM getInitialKind decls `thenM` \ initial_kinds -> + + -- Step 2 + tcExtendKindEnv initial_kinds (mappM kcTyClDecl decls) `thenM_` + + -- Step 3 + zonkKindEnv initial_kinds `thenM` \ final_kinds -> + + -- Check for loops; if any are found, bale out now + -- because the compiler itself will loop otherwise! + checkNoErrs (checkLoops scc) `thenM` \ is_rec_tycon -> + + -- Tie the knot + traceTc (text "starting" <+> ppr final_kinds) `thenM_` + fixM ( \ ~(rec_details_list, _, rec_all_tyclss) -> + -- Step 4 + let + kind_env = mkNameEnv final_kinds + rec_details = mkNameEnv rec_details_list + + -- Calculate variances, and feed into buildTyConOrClass + rec_vrcs = calcTyConArgVrcs [tc | ATyCon tc <- rec_all_tyclss] + + build_one = buildTyConOrClass is_rec_tycon kind_env + rec_vrcs rec_details + tyclss = map build_one decls + + in + -- Step 5 + -- Extend the environment with the final + -- TyCons/Classes and check the decls + tcExtendGlobalEnv tyclss $ + mappM tcTyClDecl1 decls `thenM` \ tycls_details -> + + -- Return results + getGblEnv `thenM` \ env -> + returnM (tycls_details, env, tyclss) + ) `thenM` \ (_, env, tyclss) -> + + -- Step 7: Check validity + traceTc (text "ready for validity check") `thenM_` + getModule `thenM` \ mod -> + setGblEnv env ( + mappM_ (checkValidTyCl mod) decls + ) `thenM_` + traceTc (text "done") `thenM_` + + let -- Add the tycons that come from the classes + -- We want them in the environment because + -- they are mentioned in interface files + implicit_tycons, implicit_ids, all_tyclss :: [TyThing] + implicit_tycons = [ATyCon (classTyCon clas) | AClass clas <- tyclss] + all_tyclss = implicit_tycons ++ tyclss + implicit_ids = [AnId id | id <- implicitTyThingIds all_tyclss] + new_things = implicit_ids ++ all_tyclss in - checkTc (null syn_cycles) (typeCycleErr syn_cycles) `thenTc_` - - let -- CHECK FOR CLASS CYCLES - cls_sccs = findSCCs mk_edges cls_decls - cls_cycles = [map fmt_decl (bagToList decls) - | CyclicSCC decls <- cls_sccs] + returnM (env, new_things) - in - checkTc (null cls_cycles) (classCycleErr cls_cycles) `thenTc_` - - -- DO THE MAIN DEPENDENCY ANALYSIS - let - decl_sccs = findSCCs mk_edges decls - scc_bags = map bag_acyclic decl_sccs - in - returnTc (scc_bags) - where - bag_acyclic (AcyclicSCC scc) = unitBag scc - bag_acyclic (CyclicSCC sccs) = sccs - -fmt_decl decl - = (ppr PprForUser name, getSrcLoc name) - where - name = get_name decl - get_name (TyD (TyData _ name _ _ _ _ _)) = name - get_name (TyD (TyNew _ name _ _ _ _ _)) = name - get_name (TyD (TySynonym name _ _ _)) = name - get_name (ClD (ClassDecl _ name _ _ _ _ _)) = name + decls = case scc of + AcyclicSCC decl -> [decl] + CyclicSCC decls -> decls + +tcTyClDecl1 decl + | isClassDecl decl = tcAddDeclCtxt decl (tcClassDecl1 decl) + | otherwise = tcAddDeclCtxt decl (tcTyDecl decl) + +-- We do the validity check over declarations, rather than TyThings +-- only so that we can add a nice context with tcAddDeclCtxt +checkValidTyCl this_mod decl + = tcLookupGlobal (tcdName decl) `thenM` \ thing -> + if not (isLocalThing this_mod thing) then + -- Don't bother to check validity for non-local things + returnM () + else + tcAddDeclCtxt decl $ + case thing of + ATyCon tc -> checkValidTyCon tc + AClass cl -> checkValidClass cl \end{code} -Edges in Type/Class decls -~~~~~~~~~~~~~~~~~~~~~~~~~ + +%************************************************************************ +%* * +\subsection{Step 1: Initial environment} +%* * +%************************************************************************ + \begin{code} -mk_edges (TyD (TyData ctxt name _ condecls _ _ _)) - = (uniqueOf name, set_to_bag (get_ctxt ctxt `unionUniqSets` get_cons condecls)) -mk_edges (TyD (TyNew ctxt name _ condecl _ _ _)) - = (uniqueOf name, set_to_bag (get_ctxt ctxt `unionUniqSets` get_cons condecl)) -mk_edges (TyD (TySynonym name _ rhs _)) - = (uniqueOf name, set_to_bag (get_ty rhs)) -mk_edges (ClD (ClassDecl ctxt name _ sigs _ _ _)) - = (uniqueOf name, set_to_bag (get_ctxt ctxt `unionUniqSets` get_sigs sigs)) - -get_ctxt ctxt - = unionManyUniqSets (map (set_name.fst) ctxt) - -get_cons cons - = unionManyUniqSets (map get_con cons) - where - get_con (ConDecl _ btys _) - = unionManyUniqSets (map get_bty btys) - get_con (ConOpDecl bty1 _ bty2 _) - = unionUniqSets (get_bty bty1) (get_bty bty2) - get_con (NewConDecl _ ty _) - = get_ty ty - get_con (RecConDecl _ nbtys _) - = unionManyUniqSets (map (get_bty.snd) nbtys) - - get_bty (Banged ty) = get_ty ty - get_bty (Unbanged ty) = get_ty ty - -get_ty (MonoTyVar tv) - = emptyUniqSet -get_ty (MonoTyApp name tys) - = (if isRnTyCon name then set_name name else emptyUniqSet) - `unionUniqSets` get_tys tys -get_ty (MonoFunTy ty1 ty2) - = unionUniqSets (get_ty ty1) (get_ty ty2) -get_ty (MonoListTy ty) - = get_ty ty -- careful when defining [] (,,) etc as -get_ty (MonoTupleTy tys) -- [ty] (ty,ty,ty) will not give edges! - = get_tys tys -get_ty other = panic "TcTyClsDecls:get_ty" - -get_pty (HsForAllTy _ ctxt mty) - = get_ctxt ctxt `unionUniqSets` get_ty mty -get_pty other = panic "TcTyClsDecls:get_pty" - -get_tys tys - = unionManyUniqSets (map get_ty tys) - -get_sigs sigs - = unionManyUniqSets (map get_sig sigs) - where - get_sig (ClassOpSig _ ty _ _) = get_pty ty - get_sig other = panic "TcTyClsDecls:get_sig" - -set_name name = unitUniqSet (uniqueOf name) - -set_to_bag set = listToBag (uniqSetToList set) +getInitialKind :: RenamedTyClDecl -> TcM (Name, TcKind) +getInitialKind decl + = kcHsTyVars (tyClDeclTyVars decl) `thenM` \ arg_kinds -> + newKindVar `thenM` \ result_kind -> + returnM (tcdName decl, mk_kind arg_kinds result_kind) + +mk_kind tvs_w_kinds res_kind = foldr (mkArrowKind . snd) res_kind tvs_w_kinds \end{code} -get_binders -~~~~~~~~~~~ -Extract *binding* names from type and class decls. Type variables are -bound in type, data, newtype and class declarations and the polytypes -in the class op sigs. +%************************************************************************ +%* * +\subsection{Step 2: Kind checking} +%* * +%************************************************************************ -Why do we need to grab all these type variables at once, including -those locally-quantified type variables in class op signatures? -Because we can only commit to the final kind of a type variable when -we've completed the mutually recursive group. For example: +We need to kind check all types in the mutually recursive group +before we know the kind of the type variables. For example: class C a where op :: D b => a -> b -> b @@ -288,50 +247,284 @@ Here, the kind of the locally-polymorphic type variable "b" depends on *all the uses of class D*. For example, the use of Monad c in bop's type signature means that D must have kind Type->Type. +\begin{code} +kcTyClDecl :: RenamedTyClDecl -> TcM () + +kcTyClDecl decl@(TySynonym {tcdSynRhs = rhs}) + = kcTyClDeclBody decl $ \ result_kind -> + kcHsType rhs `thenM` \ rhs_kind -> + unifyKind result_kind rhs_kind + +kcTyClDecl (ForeignType {}) = returnM () + +kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = context, tcdCons = con_decls}) + = kcTyClDeclBody decl $ \ result_kind -> + kcHsContext context `thenM_` + mappM_ kc_con_decl (visibleDataCons con_decls) + where + kc_con_decl (ConDecl _ ex_tvs ex_ctxt details loc) + = kcHsTyVars ex_tvs `thenM` \ kind_env -> + tcExtendKindEnv kind_env $ + kcConDetails new_or_data ex_ctxt details + +kcTyClDecl decl@(ClassDecl {tcdCtxt = context, tcdSigs = class_sigs}) + = kcTyClDeclBody decl $ \ result_kind -> + kcHsContext context `thenM_` + mappM_ kc_sig (filter isClassOpSig class_sigs) + where + kc_sig (ClassOpSig _ _ op_ty loc) = kcHsLiftedSigType op_ty + +kcTyClDeclBody :: RenamedTyClDecl -> (Kind -> TcM a) -> TcM a +-- Extend the env with bindings for the tyvars, taken from +-- the kind of the tycon/class. Give it to the thing inside, and +-- check the result kind matches +kcTyClDeclBody decl thing_inside + = tcAddDeclCtxt decl $ + tcLookup (tcdName decl) `thenM` \ thing -> + let + kind = case thing of + AGlobal (ATyCon tc) -> tyConKind tc + AGlobal (AClass cl) -> tyConKind (classTyCon cl) + AThing kind -> kind + -- For some odd reason, a class doesn't include its kind + + (tyvars_w_kinds, result_kind) = zipFunTys (hsTyVarNames (tyClDeclTyVars decl)) kind + in + tcExtendKindEnv tyvars_w_kinds (thing_inside result_kind) +\end{code} + + + +%************************************************************************ +%* * +\subsection{Step 4: Building the tycon/class} +%* * +%************************************************************************ \begin{code} -get_binders :: Bag Decl - -> ([RnName], -- TyVars; no dups - [(RnName, Maybe Arity)],-- Tycons; no dups; arities for synonyms - [RnName]) -- Classes; no dups +buildTyConOrClass + :: (Name -> AlgTyConFlavour -> RecFlag) -- Whether it's recursive + -> NameEnv Kind + -> FiniteMap TyCon ArgVrcs -> NameEnv TyThingDetails + -> RenamedTyClDecl -> TyThing + +buildTyConOrClass rec_tycon kenv rec_vrcs rec_details + (TySynonym {tcdName = tycon_name, tcdTyVars = tyvar_names}) + = ATyCon tycon + where + tycon = mkSynTyCon tycon_name tycon_kind arity tyvars rhs_ty argvrcs + tycon_kind = lookupNameEnv_NF kenv tycon_name + arity = length tyvar_names + tyvars = mkTyClTyVars tycon_kind tyvar_names + SynTyDetails rhs_ty = lookupNameEnv_NF rec_details tycon_name + argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon + +buildTyConOrClass rec_tycon kenv rec_vrcs rec_details + (TyData {tcdND = data_or_new, tcdName = tycon_name, + tcdTyVars = tyvar_names}) + = ATyCon tycon + where + tycon = mkAlgTyCon tycon_name tycon_kind tyvars ctxt argvrcs + data_cons sel_ids flavour + (rec_tycon tycon_name flavour) gen_info + + DataTyDetails ctxt data_cons sel_ids gen_info = lookupNameEnv_NF rec_details tycon_name + + tycon_kind = lookupNameEnv_NF kenv tycon_name + tyvars = mkTyClTyVars tycon_kind tyvar_names + argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon + + -- Watch out! mkTyConApp asks whether the tycon is a NewType, + -- so flavour has to be able to answer this question without consulting rec_details + flavour = case data_or_new of + NewType -> NewTyCon (mkNewTyConRep tycon) + DataType | all_nullary data_cons -> EnumTyCon + | otherwise -> DataTyCon + + all_nullary (DataCons cons) = all (null . dataConOrigArgTys) cons + all_nullary other = False -- Safe choice for unknown data types + -- NB (null . dataConOrigArgTys). It used to say isNullaryDataCon + -- but that looks at the *representation* arity, and that in turn + -- depends on deciding whether to unpack the args, and that + -- depends on whether it's a data type or a newtype --- so + -- in the recursive case we can get a loop. This version is simple! + +buildTyConOrClass rec_tycon kenv rec_vrcs rec_details + (ForeignType {tcdName = tycon_name, tcdExtName = tycon_ext_name}) + = ATyCon (mkForeignTyCon tycon_name tycon_ext_name liftedTypeKind 0 []) + +buildTyConOrClass rec_tycon kenv rec_vrcs rec_details + (ClassDecl {tcdName = class_name, tcdTyVars = tyvar_names, tcdFDs = fundeps} ) + = AClass clas + where + clas = mkClass class_name tyvars fds + sc_theta sc_sel_ids op_items + tycon + + tycon = mkClassTyCon tycon_name class_kind tyvars + argvrcs dict_con + clas -- Yes! It's a dictionary + flavour + (rec_tycon class_name flavour) + -- A class can be recursive, and in the case of newtypes + -- this matters. For example + -- class C a where { op :: C b => a -> b -> Int } + -- Because C has only one operation, it is represented by + -- a newtype, and it should be a *recursive* newtype. + -- [If we don't make it a recursive newtype, we'll expand the + -- newtype like a synonym, but that will lead toan inifinite type + + ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name + = lookupNameEnv_NF rec_details class_name + + class_kind = lookupNameEnv_NF kenv class_name + tyvars = mkTyClTyVars class_kind tyvar_names + argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon + + flavour = case dataConOrigArgTys dict_con of + -- The tyvars in the datacon are the same as in the class + [rep_ty] -> NewTyCon rep_ty + other -> DataTyCon + + -- We can find the functional dependencies right away, + -- and it is vital to do so. Why? Because in the next pass + -- we check for ambiguity in all the type signatures, and we + -- need the functional dependcies to be done by then + fds = [(map lookup xs, map lookup ys) | (xs,ys) <- fundeps] + tyvar_env = mkNameEnv [(varName tv, tv) | tv <- tyvars] + lookup = lookupNameEnv_NF tyvar_env + +bogusVrcs = panic "Bogus tycon arg variances" +\end{code} -get_binders decls = (bagToList tyvars, bagToList tycons, bagToList classes) +\begin{code} +mkNewTyConRep :: TyCon -- The original type constructor + -> Type -- Chosen representation type + -- (guaranteed not to be another newtype) + +-- Find the representation type for this newtype TyCon +-- Remember that the representation type is the ultimate representation +-- type, looking through other newtypes. +-- +-- The non-recursive newtypes are easy, because they look transparent +-- to splitTyConApp_maybe, but recursive ones really are represented as +-- TyConApps (see TypeRep). +-- +-- The trick is to to deal correctly with recursive newtypes +-- such as newtype T = MkT T + +mkNewTyConRep tc + = go [] tc where - (tyvars, tycons, classes) = foldBag union3 get_binders1 - (emptyBag,emptyBag,emptyBag) - decls - - union3 (a1,a2,a3) (b1,b2,b3) - = (a1 `unionBags` b1, a2 `unionBags` b2, a3 `unionBags` b3) - -get_binders1 (TyD (TyData _ name tyvars _ _ _ _)) - = (listToBag tyvars, unitBag (name,Nothing), emptyBag) -get_binders1 (TyD (TyNew _ name tyvars _ _ _ _)) - = (listToBag tyvars, unitBag (name,Nothing), emptyBag) -get_binders1 (TyD (TySynonym name tyvars _ _)) - = (listToBag tyvars, unitBag (name, Just (length tyvars)), emptyBag) -get_binders1 (ClD (ClassDecl _ name tyvar sigs _ _ _)) - = (unitBag tyvar `unionBags` sigs_tvs sigs, - emptyBag, unitBag name) - -sigs_tvs sigs = unionManyBags (map sig_tvs sigs) - where - sig_tvs (ClassOpSig _ ty _ _) = pty_tvs ty - pty_tvs (HsForAllTy tvs _ _) = listToBag tvs -- tvs doesn't include the class tyvar + -- Invariant: tc is a NewTyCon + -- tcs have been seen before + go tcs tc + | tc `elem` tcs = unitTy + | otherwise + = let + rep_ty = head (dataConOrigArgTys (head (tyConDataCons tc))) + in + case splitTyConApp_maybe rep_ty of + Nothing -> rep_ty + Just (tc', tys) | not (isNewTyCon tc') -> rep_ty + | otherwise -> go1 (tc:tcs) tc' tys + + go1 tcs tc tys = substTyWith (tyConTyVars tc) tys (go tcs tc) \end{code} +%************************************************************************ +%* * +\subsection{Dependency analysis} +%* * +%************************************************************************ +Dependency analysis +~~~~~~~~~~~~~~~~~~~ \begin{code} -typeCycleErr syn_cycles sty - = ppAboves (map (pp_cycle sty "Cycle in type declarations ...") syn_cycles) +checkLoops :: SCC RenamedTyClDecl + -> TcM (Name -> AlgTyConFlavour -> RecFlag) +-- Check for illegal loops, +-- a) type synonyms +-- b) superclass hierarchy +-- +-- Also return a function that says which tycons are recursive. +-- Remember: +-- a newtype is recursive if it is part of a recursive +-- group consisting only of newtype and synonyms + +checkLoops (AcyclicSCC _) + = returnM (\ _ _ -> NonRecursive) + +checkLoops (CyclicSCC decls) + = let -- CHECK FOR CLASS CYCLES + cls_edges = mapMaybe mkClassEdges decls + cls_cycles = findCycles cls_edges + in + mapM_ (cycleErr "class") cls_cycles `thenM_` + + let -- CHECK FOR SYNONYM CYCLES + syn_edges = map mkEdges (filter isSynDecl decls) + syn_cycles = findCycles syn_edges + in + mapM_ (cycleErr "type synonym") syn_cycles `thenM_` + + let -- CHECK FOR NEWTYPE CYCLES + newtype_edges = map mkEdges (filter is_nt_cycle_decl decls) + newtype_cycles = findCycles newtype_edges + rec_newtypes = mkNameSet [tcdName d | ds <- newtype_cycles, d <- ds] -classCycleErr cls_cycles sty - = ppAboves (map (pp_cycle sty "Cycle in class declarations ...") cls_cycles) + rec_tycon name (NewTyCon _) + | name `elemNameSet` rec_newtypes = Recursive + | otherwise = NonRecursive + rec_tycon name other_flavour = Recursive + in + returnM rec_tycon + +---------------------------------------------------- +-- A class with one op and no superclasses, or vice versa, +-- is treated just like a newtype. +-- It's a bit unclean that this test is repeated in buildTyConOrClass +is_nt_cycle_decl (TySynonym {}) = True +is_nt_cycle_decl (TyData {tcdND = NewType}) = True +is_nt_cycle_decl (ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs}) = length ctxt + length sigs == 1 +is_nt_cycle_decl other = False + +---------------------------------------------------- +findCycles edges = [ ds | CyclicSCC ds <- stronglyConnComp edges] + +---------------------------------------------------- +mkEdges :: RenamedTyClDecl -> (RenamedTyClDecl, Name, [Name]) +mkEdges decl = (decl, tyClDeclName decl, nameSetToList (tyClDeclFVs decl)) + +---------------------------------------------------- +-- mk_cls_edges looks only at the context of class decls +-- Its used when we are figuring out if there's a cycle in the +-- superclass hierarchy + +mkClassEdges :: RenamedTyClDecl -> Maybe (RenamedTyClDecl, Name, [Name]) +mkClassEdges decl@(ClassDecl {tcdCtxt = ctxt, tcdName = name}) = Just (decl, name, [c | HsClassP c _ <- ctxt]) +mkClassEdges other_decl = Nothing +\end{code} + + +%************************************************************************ +%* * +\subsection{Error management +%* * +%************************************************************************ + +\begin{code} +cycleErr :: String -> [RenamedTyClDecl] -> TcM () + +cycleErr kind_of_decl decls + = addErrAt loc (ppr_cycle kind_of_decl decls) + where + loc = tcdLoc (head decls) -pp_cycle sty str things - = ppHang (ppStr str) - 4 (ppAboves (map pp_thing things)) +ppr_cycle kind_of_decl decls + = hang (ptext SLIT("Cycle in") <+> text kind_of_decl <+> ptext SLIT("declarations:")) + 4 (vcat (map pp_decl decls)) where - pp_thing (pp_name, loc) - = ppCat [pp_name, ppr sty loc] + pp_decl decl = hsep [quotes (ppr (tcdName decl)), + ptext SLIT("at"), ppr (tcdLoc decl)] \end{code}